The present invention relates to an electrodeless discharge lamp system, more particularly, to an electrodeless discharge lamp system which is used for a tunnel lighting, a bridge lighting, and a photochemical processing device for a sewage bactericidal processing.
An electrodeless discharge lamp has a spherical or ellipsoidal glass bulb filled therein with rare earth discharge gas and metal vapor such as mercury vapor. Moreover, an excitation coil is placed near the discharge lamp. By using a high frequency power source the excitation coil induces a magnetic field alternating At 13.56 MHz. The discharge lamp is operated by the electric filed induced by the magnetic field.
A conventional electrodeless discharge lamp system is comprised of, e.g., an electrodeless discharge lamp with spherical glass bulb filled therein discharge gases such as inert gases or metal vapor and coated with either transparent or fluorescent substance on its inner surface, an excitation coil placed in proximity of the periphery of the electrodeless discharge lamp for inducing a high-frequency electromagnetic field, a high frequency power source for supplying a high frequency power to the excitation coil connected thereto, and a matching circuit for matching the excitation coil and the high frequency power source with each other so as to effectively supply the high frequency power to the electrodeless discharge lamp without line reflection.
It is known that the high frequency power source is comprised of a high frequency oscillator for supplying the high frequency power source into the excitation coil, and a DC power source for converting an AC voltage from an AC power source such as a commercial-frequency power source into a DC power voltage for driving the high frequency oscillator
A high frequency magnetic field is induced by feeding the excitation coil with a high frequency current at a several MHz to a several hundred MHz from the high frequency power source. Then, a high frequency plasma current is induced inside the electrodeless discharge lamp, and the ultraviolet ray or the visible light is emitted
On the other hand, in the conventional electrodeless discharge lamp, impedances of the excitation coil and the electrodeless discharge lamp vary from moment to moment in a while in a transient period from a start of operation till reaching a stable operation. Therefore, according to the change of these impedances, it is necessary to match the impedance of the high frequency power source to that of the excitation coil by adjusting at least the output impedance of the high frequency power source.
For this reason, as an electrodeless discharge lamp system which is capable of transmitting a high frequency power with a high degree of efficiency even though a load condition in tho electrodeless discharge lamp varies, there is proposed an electrodeless discharge lamp system comprised of, e.g., a high frequency power excitation coil coupled across the output terminals of the high frequency power source, an electrodeless discharge lamp filled with discharge gases such as inert gases and metal vapor in its glass bulb, placed in proximity of the high frequency power excitation coil, a first matching circuit connected between the high frequency power source and the high frequency power excitation coil, a coaxial cable connecting the high frequency power source and the first matching circuit, and a second matching circuit connecting the coaxial cable and the high frequency power source in the Japan Unexamined Patent Publication (Kokai) H6-310291.
In the electrodeless discharge lamp system with the above configuration, the coaxial cable is used in matching with the characteristic impedance of the lamp system. As a consequence, the coaxial cable advantageously exerts a high efficiency of power transmission. Moreover, the Japan Unexamined Patent Publication (Kokai) H6-310291 shows a configuration for adjusting operating conditions of the high frequency power source by varying driving DC brass of switching elements of the high frequency power source on and after starting the operation of the electrodeless discharge lamp.
On the other hand, the conventional electrodeless discharge lamp system can be modified to have multiple parallel-connected high frequency power sources, i.e., DC-RF power converters and combine their outputs for transmitting them to its load, i.e., an electrodeless discharge lamp via a transmission line. According to the configuration, it is able to achieve the operation and effect an described above, and it is also able to use power converters with a relatively small power capacity. Therefore, the development of the system becomes easy and be reduced its duration, as well as reduced its manufacturing cost.
However, matters to be considered for changing operating conditions differ between a configuration where only one high frequency power source is subjected for the change of operating conditions like the conventional electrodeless discharge lamp system and a configuration where multiple parallel-connected high frequency power sources of supplying a combined power to a load, i.e., an electrodeless discharge lamp are subjected for the change of operating conditions, as described above. For instance, in the configuration of operating multiple parallel-connected power sources, the operation power increases in proportion to the number of power sources. When these power sources operate in asynchronization with each other, there arises a drawback of upsizing the combiner. That is, such a configuration of combining powers of multiple parallel-connected high frequency power source (DC-RF power converting circuit) is able to improve the power conversion efficiency at a low cost much more than the configuration of supplying a bulk power from only one high frequency power source. However, since it is necessary to deal with a bulk power in a single matching circuit like the conventional device, there arises a drawback that the circuit efficiency and cost efficiency reduce in the matching circuit.
To solve the above drawbacks, inventors have developed an electrodeless discharge lamp system which is comprised of an electrodeless discharge lamp, an excitation coil placed in the proximity along the electrodeless discharge lamp, a resonance circuit for supplying an appropriate power to the excitation coil, a high frequency power source for supplying a combined output of multiple parallel-connected power sources to the resonance circuit, and a driver of the high frequency power source, as a result of several researches and studies The inventors have ascertain that in such an electrodeless discharge lamp system since a combined output of the multiple parallel-connected power sources may be achieved by driven in synchronization or approximately in synchronization with each other, a magnetic flux induced by one power output may be counteracted by other magnetic flux induced by the other power output in the combiner. Therefore, the inventors have also ascertained that since the magnetic fluxes inside a magnetic core utilized in a combiner may counteract each other, and thus core-losses may be reduced in the combiner, the combiner may be miniaturized at a low cost.
Here, as described above, since the operation power of the driver which works as a switching element in the parallel-connected high frequency power sources increases in proportion to the number of an amplifier comprising the power source, the rise in the number of the amplifier without the change of threshold for turning on and off the switching element causes drawback of decreasing a operating voltage of the switching element. So, the inventors have ascertained that if the DC voltage is superposed on the output of the driver for the switching element, the parallel-connected power sources may be driven in a relatively small driver.
On the other hand, the inventors have also ascertained that in case of operating multiple parallel-connected DC-RF power converters in synchronization or approximately in synchronization with each other as the high frequency power source, if the electrodeless discharge lamp system is provided with a combiner for combining output from the parallel connected DC-RF power converters, a matching circuit for matching a condition of the excitation coil for feeding the power to the electrodeless discharge lamp, and a transmission line for transmitting a power to the matching circuit from the combiner, matching circuits of relatively small capacity arc provided in a distributed manner without placing a matching circuit collects a bulk power at the input end of the transmission line, thus resulted in achievement of a low-cost high frequency power source and a highly efficient power transmission through the transmission line.
That is, the inventors have ascertained that when the output combined impedance (Zamp-Out) of N-piece parallel-connected DC-RF power converters to the characteristic impedance (Ztl) of the transmission line is defined by a following equation, low-cost high frequency power source and a highly efficient power transmission of the transmission line are achieved.
Zamp-out=Nxc2x7Ztl
Further, in a conventional bactericidal electrodeless discharge lamp system wherein multiple electrodeless discharge lamps were provided in a bactericidal tank, it could take either one of following configurations to achieve a bulk power high frequency signal; a configuration where a reference clock generator is provided for each high frequency power source for each electrodeless discharge lamp and amplified to achieve a bulk power high frequency signal, or a configuration where a clock signal is shared by multiple high frequency power sources in a specific enclosure and supplied for multiple high frequency amplifiers for achieving a bulk power high frequency signal. However, in the former configuration there arises a drawback that an electric field coupling is caused among these electrodeless discharge lamps, thus minute frequency errors of the reference clock causes flickers of the discharge lamp. On the other hand, in the later configuration a phase delay of the reference clock is caused in the power receiving terminal of each high frequency power source while transmitting the reference clock through the cable. Thus, there arises a drawback that when a bulk power high frequency signal achieved by amplifying the clock signal in supplied to each electrodeless discharge lamp, phase differences among powers applied to each electrodeless discharge lamp causes flickers of the discharge lamp.
In order to solve these drawbacks as described above, the inventors have ascertained that in case of connecting multiple high frequency power sources to a reference clock generator in parallel via the coaxial cables for reference clock, the high frequency power source outputs agree in phase with each other by agreeing the lengths of these coaxial cables with each other, thus resulted in prevention of flickers of the discharge lamp.
Further, the inventors have also ascertained that in case of cascading each high frequency power source to the reference clock generator in sequence via the coaxial cables for reference clock, by defining the lengths of the coaxial cable to make the reference clocks of the reference clock input terminal of each high frequency power source or the high frequency power source outputs agree in phase with each other, thus resulted in prevention of flickers of the discharge lamp.
On the other hand, in the bactericidal electrodeless discharge lamp system wherein multiple electrodeless discharge lamps are placed in one bactericidal tank, it is possible to prevent flickers of the discharge lamps by operating multiple high frequency power source with an output applied from a signal reference oscillator. However, if DC voltages are determined in each high frequency power source based on the reference voltage, the intensity of The emitted light varies among electrodeless discharge lamp.
In order to solve the problems, the inventors have ascertained that by supplying only one external dimming signal to the DC power source for supplying DC voltages to each high frequency power source so as to determine these DC voltages as a single unit, thus resulted in prevention of variations in intensity of the emitted lights of the discharge lamps. In this case, for determining DC voltages as a single unit, a photosensor is provided in the bactericidal tank and then a DC voltage in proportion to the amount or an intensity of light detected by the photosensor can be used for determining the DC voltages as a single unit Further, as another way of determining the DC voltages as a single unit, it is able to use the amount of power, which is detectable from the electrodeless discharge lamp system itself, e.g., an output from any high frequency power source by fed back without using the signal from external such as a photosensor.
In addition, in the conventional electrodeless discharge lamp system, the high frequency power source is comprised of a main amplifier and a preamplifer for driving the main amplifier, which are connected directly with a printed wiring. Accordingly, in addition to a difficulty of executing individually an evaluation and a verification of these amplifiers, there was a drawback of lacking versatility for the circuit arrangement of these amplifiers.
To solve this drawback, the inventors have ascertained that by coupling the main amplifier and the preamplifier for driving the main amplifier via a coaxial cable, the flexibility of the block arrangement in an assembling process will increase, thus resulted in ease of verifying characteristics in every block. In this cases it is able to provide a distributor in every block comprised of multiple main amplifiers, and connect a preamplifier to the distributor via a coaxial cable. On the other hand, it is able to provide a distributor in every block comprised of the preamplifier, and connect multiple main amplifiers to the distributor via coaxial cable.
Further, in case of a high frequency power source for generating high frequency power which drives the electrodeless discharge lamps comprising a plurality of parallel power converters, it is able to provide a combiner for combining outputs from these power converters via a balance resistor. Furthermore, it could also define a distributor for distributing inputs to each power converter via s balance resistor.
In the former configuration, the inventors have ascertained that while one of the output terminal of the power converters is opened, short-circuited or no signal input, by getting the rated power of each balance resistor in the combiner for combining outputs of parallel-connected power converters to a value that the output terminal of other power converters can not stand, the electrodeless discharge lamp system may be operated appropriately even in the state where the high frequency power of the high frequency power source decreased by a large amount.
Similarly, in the latter configuration, while one of the output terminal of the power converters is opened, short-circuited or no signal input, the rated power of the balance resistor in the distributor for distributing input to each power converters may be to a value that the output terminal of other power converters can not stand. In such cases, by placing the distributor or combiner on the extension of or equidistantly from the parallel-connected power converters, it is able to prevent the phase difference among their inputs and reduce an adverse effect to the combined output.
Further, when the parallel-connected power converters as the high frequency power sources are divided into multiple blocks and a combiner is provided in each block so as to combine powers of the power converters in each block, it is able to provide an impedance converter between these combiners in order to execute appropriate impedance conversion. However, in this case, there arises a drawback such as a combiner loss caused by the variations of components or an excessive temperature rise in the impedance conversion after the last combining caused by the power concentration.
So, the inventors have ascertained that by combining the powers of every two power converters in a combiner, and converting the impedance of the combined power into a characteristic impedance of the transmission cable to the electrodeless discharge lamp using a xcex/4 transmission line, it is able to reduce the coat of components, the combiner loss, and the variation in conversion of the power converter among the parallel-connected circuits.
Furthermore, when the powers of multiple parallel-connected power converters as a high frequency power source are combined in the combiner, if phase changes occur in the output powers of the power converter, a combiner loss will increase. In order to prevent such a combiner loss, components of respective power converters are aligned roughly in a row, and these power converter are coupled in parallel with each other for achieving a high-density arrangement. However, in such an arrangement, since coils, which constitute an inductor of each series LC resonance filter, are aligned in parallel with each other, the spaces between these coils are lesson in case of reducing the mounting area ever further for the high-density arrangement. Thus, these coils interfere with each other so as to change the filter constant.
The inventors have ascertained that when each power converter is comprised of field-effect transistors (hereinafter, referred to as FETs or FET) and a series LC resonance filter for a class-E operation, where the FETs are arranged in parallel with each other, and the coils constituting the inductor of the series LC resonance filter are arranged in parallel with each other and in a slanting position against the corresponding FETs, it is able to reduce the mutual interference and achieve a high-density arrangement of components.
If the impedance which is a load of the electrodeless discharge lamp varies, it will mismatch to the output impedance of the high frequency power source. To correct the mismatch, the inventors have ascertained that by detecting a phase angle of the high frequency power source output and feeding back the phase angle so as to change the frequency of the high frequency power source, it is able to adjust a load impedance, i.e., the impedance of the electrodeless discharge lamp, and furthermore by detecting the change of the output power caused by the frequency change at the impedance adjustment and feeding back the amount of changing so as to control the power source voltage of the high frequency power source, it is able to adjust the load impedance, i.e., the impedance of the electrodeless discharge lamp and the output impedance of the high frequency power source, thus resulted in that the output power is regulated in constant.
Accordingly, it is an abject of the present invention to provide an electrodeless discharge lamp system, which is able to simplify the configuration of the high frequency power source for the electrodeless discharge lamp, and which can reduce the cost of manufacturing, and enhance the efficiency of power.
In order to achieve the object, the electrodeless discharge lamp system according to the present invention is comprised of an electrodeless discharge lamp, an excitation coil placed in proximity to the electrodeless discharge lamp, a resonance circuit for supplying appropriate power to the excitation coil, a high frequency power source for supplying a combined output of the parallel-connected power sources, and a high frequency power source driver, and wherein, the combined output is achieved by operating the parallel-connected power sources in synchronization or approximately in synchronization with each other.
In this case, the system may also be provided with a DC voltage superposing circuit for superposing a DC voltage to the output of the driver of the high frequency power source. Then, the DC voltage may be adjustable in the DC voltage superposing circuit.
Moreover, the DC voltage superposing circuit may be so constructed to generate a mean voltage by executing a half-wave rectification on the output of the high frequency power source.
On the other hand, the electrodes discharge lamp system may be comprised of an electrodeless discharge lamp, an excitation coil which is placed in proximity to the electrodeless discharge lamp, a matching circuit for matching conditions of the excitation coil for supplying the power to the electrodeless discharge lamp, a DC-RF power converters which are connected in some parallel arrangements to operate in synchronization or approximately in synchronization with each other, a combiner for combining outputs from the parallel-connected power converters, and a transmission line for transmitting the power from the combiner to the matching circuit.
In this configuration, the output combined impedance (Zamp-out) of the DC-RF power converters which are connected in some parallel arrangements (N parallel arrangements) to the characteristic impedance of the transmission line (Ztl) may be set to become the following equation.
Zamp-out=Nxc2x7Ztl
The electrodeless discharge lamp system may be comprised of multiple electrodeless discharge lamp, excitation coils placed in proximity of these electrodeless discharge lamp multiple electrodeless discharge lamp units, each of which is comprised of a matching circuit for supplying an appropriate power to each excitation coil, high frequency power sources, which input a reference clock signal from the outside sources and amplify it so as to supply the high frequency power to the electrodeless discharge lamp units via a coaxial cable, and a reference clock generator, which is connected to each high frequency power sources in parallel via coaxial cables, for generating a single reference clock signal to he high frequency power sources. Here, the lengths of the coaxial cables connecting the reference clock generator and each high frequency power sources may be agreed with each other.
On the other hand, in the electrodeless discharge lamp system, it is also able to take a configuration of having a reference clock generator which cascades the high frequency power sources via a coaxial cables for generating a single reference clock signal to these high frequency power sources. In this case, the length of each coaxial cable may be agreed with each other so as to make the reference clocks of the reference clock input terminal of each high frequency power source or the high frequency power source output are agreed in phase with each other.
As an alternative configuration, an electrodeless discharge lamp system may be comprised of multiple electrodeless discharge lamps, excitation coils placed in proximity of these electrodeless discharge lamps, a bactericidal device which is provided with multiple electrodeless discharge lamps in a bactericidal tank which has multiple electrodeless discharge lamp units of the matching circuit for supplying the appropriate power to these excitation coils, high frequency power sources to supply the high frequency power to these electrodeless discharge lamp units, and DC power sources fur supplying DC voltages to these high frequency power sources. Here, these DC power sources could determine the DC voltages supplied to each high frequency power source as a single unit by applied with only one external dimming signal.
In this case, by setting a feedback signal for determining the output DC voltage of each DC power source based on the amount of power which is detectable from the electrodeless discharge lamp system itself, it is able to determine the DC voltages as a single unit.
Further, the electrodeless discharge lamp system may be comprised of an electrodeless discharge lamp, excitation coils for supplying tho high frequency power to the electrodeless discharge lamp, a high frequency power source for generating the high frequency power, a high frequency power source driver, and an output circuit for outputting the high frequency power of the high frequency power source to the excitation coils. Here, the high frequency power source is comprised of main amplifiers and a preamplifier for driving the main amplifier, which are connected with each other via a coaxial cable
In this case, a distributor is provided in a block of multiple main amplifiers, and the preamplifier may be connected to the distributor via a coaxial cable. Further, the distributor may be provided in a block of the preamplifier and the distributor may be connected to the main amplifiers via coaxial cable.
On the other hand, the electrodeless discharge lamp system may be comprised of an electrodeless discharge lamp, excitation coils for supplying the high frequency power to the electrodeless discharge lamp a high frequency power source comprised of multiple parallel-connected power converters for generating the high frequency power, a high frequency power source driver, an output circuit for outputting the high frequency power of the high frequency power source to the excitation coils, and a combiner comprised of a resistor and combiner for combining the parallel output of the power converters. Here, while one of the output terminal of the power converters is opened, short-circuited or no signal input, the rated power of the balance resistors in the combiner may be set to a value that the output terminal of other power converters can not stand.
It is also able to provide a distributor comprised of a distributor for distributing the parallel inputs of the power converters and a balance resistor. In this configuration, while one of the output terminal of the power converters is opened, short-circuited or no signal input, the rated power of the balance resistor in the distributor for distributing the input to the power converters may be set to a value that the output terminal of other power converters can not stand. In such cause, by placing the distributor or combiner an the extension of or equidistantly from the parallel-connected power converters, it can prevent the phase differences among their inputs and reduce an adverse effect to the combined output.
Furthermore, the electrodeless discharge lamp system may be comprised of an electrodeless discharge lamp, an excitation coil for supplying the high frequency power to the electrodeless discharge lamp, a high frequency power source comprised of parallel power converters for generating the high frequency power, a high frequency power source driver, and au output circuit for outputting the high frequency power of the high frequency power converter to the excitation coils, and herein the power of every two power converters is combined in a combiner, and the impedance of the combined power is converted into a characteristic impedance of a transmission cable to the electrodeless discharge lamp using a xcex/4 transmission line.
The electrodeless discharge lamp system may be comprised of an electrodeless discharge lamp, an excitation coil for supplying a high frequency power to the electrodeless discharge lamp, a high frequency power source comprised of parallel power converters for generating the high frequency power, a high frequency power source driver, an output circuit for outputting the high frequency power of the high frequency power source to the excitation coils, an FET, and a series LC resonance filter for a class-E operation. Here, the FETs are arranged in parallel with each other, and the coils which constitute the inductor of the series LC resonance filter are arranged in parallel with each other and in a slanting position against the corresponding FETs.
The electrodeless discharge lamp system may be comprised of an electrodeless discharge lamp, excitation coils for supplying high frequency powers to the electrodeless discharge lamp, a high frequency power source for generating the high frequency power, a high frequency power source driver, and an output circuit for outputting the high frequency power of the high frequency power source to the excitation coils. Here, by detecting a phase angle of the high frequency power source output and feeding back the phase angle so as to change the frequency of the high frequency power source, it could adjust the impedance which is the load of the electrodeless discharge lamp. Further, by detecting the change of the output power caused by the frequency change at the impedance adjustment and feeding back the amount of changing so as to control the power source voltage of the high frequency power source, it could adjust the impedance which is the load of the electrodeless discharge lamp and the output impedance of the high frequency power source. Thus, the output power may be regulated.
Additional objects and advantages of the present invention will be apparent to person skilled in the art from a study of the following description and the accompanying drawings, which are hereby incorporated in and constitute a part of this specification.